CHICAGO - As the United States bakes in one of the hottest summers since the Dust Bowl years of the 1930s, drought from the Dakotas to Arizona through Alabama has sharpened the focus of farmers on their lifeline: water.

Eighty percent of all fresh water consumed in the United States is used to produce food. But years of drought, diversion of water to growing urban areas and, most lately, concerns about global warming are feeding worries.

Specifically, farmers fear the U.S. Plains is facing its limits as a world producer of wheat, beef, vegetable oils and other crops due to long-term water shortages.

"Farmers aren't going to be able to produce enough food to feed the world because there's a finite amount of water left in the world. There are many folks that will tell you the next war will not be over gold, silver or land, it will be over water," said Ed Burchfield, director of facilities for Valmont Industries, which makes irrigation equipment.

The U.S. National Weather Service's outlook through October saw persistent drought from eastern Montana to Minnesota and on down through Nebraska, Kansas, Oklahoma and Texas -- the main spring-wheat and winter-wheat growing areas of the United States as well as its main cattle and beef production region.

"Relief for water supplies will likely need to wait until next winter's snow season, at the earliest, since snow melt is the major source for water in the West," the National Weather Service's Drought Outlook said last month.


The region under the greatest stress is the Great Plains, an area from North Dakota to Texas dubbed the Great American Desert by early explorers but turned into a garden spot in the last century thanks to a single innovation: irrigation.

But farmers from Nebraska through northern Texas are now growing more water-thirsty crops, like corn, that offer them better cash returns due to changing trends such as the boom in ethanol and biodiesel fuels.

That is only accelerating the depletion of ground water faster than it can be replenished by rain. In some cases, farm land is already being idled to conserve water.

"My sense in looking at these issues for 20 years, we're going to need at least a doubling of water productivity in agriculture if we're going to have an opportunity to meet food demand in a way that is somewhat environmentally sustainable," said Sandra Postel with the Global Water Policy Project, a group in Amherst, Massachusetts that analyzes water policies.


Experts say water scarcity will be a growing dilemma for world farmers. Most projections put world population at about 8 billion people by 2025, or another 2 billion mouths to feed.

But those people and their industries will also need more water. A 2002 study by the International Food Policy Research Institute estimated that farmers' use of irrigation water worldwide will rise only 4 percent from 1995 to 2025, partially because the water won't be available.

Meanwhile, non-irrigation water use could rise 62 percent.

"In the face of water scarcity, farmers will find themselves unable to raise crop yields as quickly as in the past, and by 2025 their irrigated cereal production will be 300 million metric tons less than it would have been with adequate water -- a difference nearly as large as the U.S. cereal crop in 2000," the study said.

But U.S. water problems have the greatest implications for world food supplies. The United States for decades has been the planet's "food reserve," the top exporter of wheat, corn and soybeans and the largest single provider of food aid to other nations.

The squeeze on water for U.S. farms is pushing innovation, such as a trend away from flood irrigation to center pivot sprinklers or state-of-the art, localized drip irrigation.

"Just the changing of irrigation techniques can save a lot of water. That's the first place to start," said Thomas Kimmell, executive director with the Irrigation Association.

Such technology is what arid Texas is banking on to maintain crop production. But further north, water costs and conflicts over the vast but shrinking Ogallala aquifer have already prompted restrictions on irrigation.

The aquifer is an 800-mile-long (1,287-km-long) underground pool that stretches from Texas to South Dakota and feeds one-fifth of all the irrigated land in the United States. But Nebraska has put a moratorium on new wells and taken farmland out of production in the Platte River Valley to limit the draw on the Ogallala.

"Farmers who constructed an irrigation well here 20 years ago did that believing that they'd never have to experience regulation of their wells," said Michael Jess, former director of Nebraska's water resources department.

"Changing the rules will adversely affect their economic situation," he said.